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How to place circles that there will be no gap. Use least number of circles possible.

by Firewolffzc
Tags: circle
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Firewolffzc
#1
Apr21-12, 02:34 PM
P: 7
I have to plan the layout of a sprinkler system. Basically, each sprinkler shoots a radius of 7.5 feet water, and I want every part of the floor covered with water. How can I use the least number of sprinklers?
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tiny-tim
#2
Apr21-12, 02:52 PM
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Hi Firewolffzc! Welcome to PF!

Tell us what you think, and then we'll comment!
Firewolffzc
#3
Apr21-12, 02:54 PM
P: 7
Well, I think I figured one way to approach. Is it better to imagine not the circle, but a triangle, square or hexagon inscribed within the circle, because these shapes can link without gaps. Then once done with these shapes, I draw a circle circumscribing the shape. I was wondering if this was an effective method. If it is, which shape is best?

tiny-tim
#4
Apr21-12, 03:02 PM
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How to place circles that there will be no gap. Use least number of circles possible.

yup, that seems a good idea!
i'd guess it's the hexagon, but you'd better do the maths!
Firewolffzc
#5
Apr22-12, 11:52 AM
P: 7
Well, see, I don't know what math to do! I figured out that the reason we can use triangles, squares and hexagons is because the measurement of their angles are multiples of 360. (triangle)60*6=360, (square)90*4=360, (hexagon)120*3= 360. Well, it is not possible to have a shape with a 180 or 360 degrees angle, therefore hexagons are the best shape because they make the smallest area between circles. Wow, I can't believe I figured that out myself. Anyway, is there more to it or is this the final solution?
tiny-tim
#6
Apr22-12, 01:55 PM
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no, that seems fine, so long as you actually prove
Quote Quote by Firewolffzc View Post
hexagons are the best shape because they make the smallest area between circles.
willem2
#7
Apr22-12, 05:20 PM
P: 1,395
A hexagonal packing might be the best for covering the entire plane (not sure), but for finite size rooms, an irregular packing can do better

This is a page with the best known results for covering a square with circles

http://www2.stetson.edu/~efriedma/circovsqu/
tiny-tim
#8
Apr22-12, 06:03 PM
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cool!
Firewolffzc
#9
Apr23-12, 06:38 PM
P: 7
Thanks for all your help. Btw, I don't know how to prove something like the area formed between circles circumscribing hexagons is the smallest compared to triangles and squares.


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